1. Field of the Invention
The present invention relates to a battery, and more particularly, to a battery configured in such a manner that an electrode plate group, which is formed by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween, is housed in a battery case together with an electrolyte solution.
2. Description of Related Art
Electric vehicles and hybrid cars are raising expectations in recent years for solving global environmental issues, and rechargeable batteries, as their power sources, are eagerly anticipated to meet demands for higher capacity and higher output capabilities in addition to downsizing and weight-saving properties. As the rechargeable batteries which meet such demands, a lithium ion rechargeable battery, a nickel-metal hydride battery, and the like have been already put into practical use.
For example, Japanese Patent Laid-Open Publication No. Hei 10-261427 discloses a battery in which an electrode plate group, formed by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween, is housed in a battery case together with an electrolyte solution. The structure of a typical battery 30 will be described below with reference to FIG. 7. Here, an electrode plate group 32 formed by winding a positive electrode plate 34 and a negative electrode plate 35 with a separator 36 interposed therebetween is housed in a battery case 31 of a prismatic shape such that a core of the roll is aligned parallel to an opening of the battery case 31. Then the opening of the battery case 31 is hermetically sealed with a lid 37 including a negative terminal 38 and a safety vent 39. A core member of the positive electrode plate 34 at the outermost periphery of the electrode plate group 32 is exposed and connected to the battery case 31; meanwhile, an end portion of the negative electrode plate 35 is connected to the negative terminal 38 with a lead 40.
Meanwhile, Japanese Patent Laid-Open Publication No. Hei 9-115500 discloses a structure for attaching a connection terminal to a lid of a battery. The structure will be described with reference to FIG. 8. A connection terminal 51 includes a pole 52 penetrating a lid 50, and a flange 53 abutting on an inner side surface of the lid 50. A sealing member 54 such as an O-ring is placed between the flange 53 and an inner surface of the lid 50, and an annular push spring 55 engaged with an outer periphery of the pole 52 is pressed to contact with an outer surface of the lid 50 via a washer 56. Accordingly, the connection terminal 51 is fixed to the lid 50 by pressure from the annular push spring 55.
However, in the structure of the battery 30 shown in FIG. 7, large force acts on the electrode plate group 32 when vibration is applied to the battery 30. Accordingly, the low-strength electrode plate group 32 suffers damage such as falling of electrode mixtures originally applied to the positive electrode plate 34 or the negative electrode plate 35, whereby battery characteristics may be suddenly deteriorated. Such a problem is critical to any batteries other than a cylindrical battery that houses a roundly wound electrode plate group in a cylindrical battery case.
Moreover, in the structure for attaching a connection terminal shown in FIG. 8, a sealing performance of the sealing member 54 is deteriorated due to variation in the amount of compression of the sealing member 54 if a fitting angle of the pole 52 of the connection terminal 51 is not perpendicular to the inner side surface of the lid 50. Accordingly, a sealing performance of the battery is deteriorated and the battery life is shortened.